Abstract
Lotus japonicus, a model legume, accumulates 8-hydroxyflavonol derivatives which are responsible for the yellow color of flower petals. From L. japonicus petals, we had purified a flavonol glycoside, gossypin, which on hydrolysis yielded the aglycone, 8-hydroxyquercetin. A recent study showed that flavonoid 8-hydroxylase in Asteraceae is localized in the microsomal fraction and uses NADPH and FAD as cofactors, but there has been no report on the identification of flavonoid 8-hydroxylase. Thus, we attempted to isolate a cDNA of flavonoid 8-hydroxylase from L. japonicus.
To isolate cDNA, we searched EST data and have selected an FAD-containing monooxygenase-like protein which was only found in EST data derived from flower buds. The heterologously expressed protein catalyzes the C-8 hydroxylation of flavonol, quercetin. This is the first identification of a flavonoid 8-hydroxylase cDNA from any plant species, and also this enzyme is a novel type of flavonoid hydroxylase. We will discuss its catalytic properties in this annual meeting.
